Early Medieval stone building began earlier and was more widespread than previously thought. This conclusion is the result of scientific dating that challenges traditional views of the “petrification” process in architecture north of the Alps after the Roman period. Radiocarbon (14C) dating is not precise enough to answer detailed questions connected to historical contexts, but recently there have been a number of surprising dates: “Roman” city walls have now Early Medieval phases or meter-high, obscure “dark earth” strata were subdivided and dated. Results not in line with clients’ expectations can be the subject of heated debates, or worse, tend to remain unpublished. To the archaeologist, who is trying to connect scientific dates with historical events, usually is not clear, that mortar dating is a methodology still being developed, while dating organic material like charcoal from mortar is a standard procedure. But even the latter has downfalls like the possible “old-wood-effect,” if such complications are not carefully considered and avoided during the sampling process. Drawing on examples from Switzerland, Germany, Austria, and France, recent challenging results will be discussed from an archaeologist’s point of view.